Of all the stupid places to put a manhole Burrell got first prize for the daftest! Even if it were big enough in scale size to be of any use it's under all the motion work so that would have to be removed first. To actually put a real manhole there would be more of a liability than any practical use so there is a token dummy one there so it has the appearance of the full size. On my 4" I glued dummy rivet heads around the oval ring to make it look a bit more realistic. No doubt someone at Burrells thought that was the best place to put one, I don't think any other manufacturer did though.RegardsSteve